1. Field of the Invention
The present invention relates to a map information processing apparatus, a map update information storage medium, a map update information data structure, a map update information creating system, and a map information updating system.
2. Description of Related Art
A prior art system, such as a navigation apparatus, that provides the user with map information for the user's convenience is known. Such a prior art system needs to revise map information at fixed intervals according to changes in roads with respect to time, and always needs to provide the user with the latest map information. To this end, there has been provided an apparatus for updating map information based on difference information about road maps (see patent reference 1, for example).
This prior art apparatus for updating map information based on difference information about road maps receives difference map information containing update data from a map transmitting means, such as a map data supply server, and stores the difference map information as received map information. The prior art apparatus then compares the received map information with previous map information, and determines which portion of the previous map information is to be updated and then extracts the determined portion as inherent difference map information. The prior art apparatus creates and outputs new map information by applying the inherent difference map information to the previous map information. Thus, since the prior art apparatus for updating map information based on difference information about road maps, which is the receiving side, can flexibly select data which should be applied to the previous map information, the map transmitting means, which is the transmitting side, need not grasp the update condition of the terminal equipment correctly. Since the prior art apparatus does not have to carryout fine control of the version of the difference map information, the structure of the prior art apparatus can be simplified.    [Patent reference 1] Japanese patent application publication (TOKKAI) No. 2002-296042
The technique disclosed by above-mentioned patent reference 1 has the following problems when further upgrading the map information which has been upgraded once according to changes in the map information which have occurred after the previous upgrading. In accordance with the prior art technique, the map transmitting means transmits changes in the map information which have occurred until now after a past time to the prior art apparatus for updating map information based on difference information about road maps at once. The prior art apparatus then compares all the received changes in the map information with map information being held thereby so as to extract a difference between all the received changes and the currently-held map information from all the received changes, and then combines the extracted information and the currently-held map information so as to update the currently-held map information.
When updating the currently-held map information, the prior art apparatus for updating map information based on difference information about road maps performs comparison between all the received changes in the map information and the map information being held thereby for each of components, such as roads and buildings. When performing comparison for each component included in the received change information, the prior art apparatus determines whether the component in question is the same as one of all components of the currently-held map information based on the lasting attributes of all the components of the currently-held map information. The lasting attributes of each component include a road shape, a road name, a route number, a VICS (Vehicle Information and Communication System) link number, names of intersecting roads, intersection names, etc.
However, there is no guarantee that these attributes are lasting, and therefore it can be predicted that the comparison between all the received changes in the map information and the map information being held by the prior art apparatus becomes difficult. A further problem is that it takes much time for the prior art apparatus to perform the comparison between all the received changes in the map information and the map information being held thereby.